Dear Treggers, This is a follow-up of the question I raised on TREG at the beginning of April, 1997.
I have since been in touch with Herr Ernst Hussinger of the German BAPT and here are the answers which I quote from his written reply: "In our new regulation BAPT 223 ZV 5 is no requirement for TEs with extended wires a2/b2 in opposite to the old regulation FTZ 1 TR 2. That implies that a relay for loop current detection is not any longer required." In a telephone conversation, in which I pressed my original point, Herr Hussinger responded that the unswitched connection by a TE of the a and a2 wires and b and b2 wires is entirely unacceptable because it would mean allowing two TEs to be connected in parallel. So the answer to my question, regardless of what is, or is not stated in BAPT 223 ZV 5 is that a TE need not support the a2/b2 connections, but that if a TE does support the a2/b2 connections, it must disconnect the a wire from the a2 wire, and the b wire from the b2 wire, when it is in the active (off-hook) state. Therefore, it seems we cannot eliminate the costly relay used for disconnecting upstream TEs. Regards, David Drori >Dear David, Regardless of whether it is allowed or not, the practical implementation of the wiring inside homes is such that parallel connections are difficult to create. Germany has a wall connector featuring three sockets. The middle one is coded 'F' which is supposed to be the phone. The two outer ones are coded 'N' for equipment that would be inserted between the line and the phone (series connection) By inserting an N-connector the line to the phone is interrupted and must be looped through the series connected equipment. This means that the only way to continue using the existing wiring in the house AND be parallel connected is to loop the wires through the modem anyway,though not using a relay but just shorting the wires together at the line connector. One would effectively change the interface from a 2 wire to four wire series connected, without the capability to interrupt the loopback to the phone. I don't know whether this is legal or acceptable, I have always done either 2 wire interfaces or 4 wire interfaces with a relay as usual, so I figured the above would be interesting to know (if you didn't already) because there is more to this then just the question legally possible or not. Best regards, Rene [Debets] ---------- From: [email protected] on behalf of David Drori Sent: Monday, April 07, 1997 2:44 PM To: TREG Subject: No Parallel Telephone Equipment for Germany? Dear Treggers, It has always been German practice to install analog telephone equipment in series; never in parallel. However, the BAPT 223 ZV 5 Standard "Approval Regulation for Terminal Equipment to be Connected to Analog Dial-up Terminals in the PSTN/ISDN of Deutsche Bundespost Telekom", appears not to stipulate that all terminal equipment be connected in series. The requirement (if it exists) that the modem disconnect any downstream equipment when the modem is active, considerably adds to the cost of the interface circuit. However, many low-cost data modems used in other parts of the world do not disconnect downstream equipment because of the expense involved. Joe Randolph's treatise entitled: "German Telecom Requirements", published most recently in his excellent series of articles about European requirements in Compliance Engineering's 1996 Reference Guide, states: "In ZV5, all TEs are considered to be two wire devices. This means that modems and answering machines may now use the same simple two-wire A/B connection that telephones use. Unfortunately, this leaves a gap in the present regulations for Germany. Since parallel connections is still not allowed in that country, a modem with a two-wire interface and a phone with a two-wire interface cannot be connected in parallel on the same phone line." I am aware of the DIN 44015 addressing this particular issue; however, my understanding is that compliance with DIN 44015 is purely on a voluntary basis. Can anyone tell me whether there is a compulsory German Standard that requires a data modem to disconnect other equipment, and point out the relevant paragraph? If I implement a least-cost design that allows for the user to share the line between his telephone set and data modem, and I am prepared to permit modem communications to be disrupted if the handset is lifted during a data call, would this actually violate any Standard, and/or prevent the modem from being sold on the German market for one reason or another? Thanks in advance for all answers received. Best regards, David Drori --------------------------------------------------------------------------- Novarex Enterprises Ltd., POB 2833, Jerusalem 91028, Israel. Tel: +972 2 581 0995 Fax: +972 2 581 3750 Mobile: +972 5 067 8686 E-mail: [email protected] --------------------------------------------------------------------------- [End of message]
